<?php

require_once('../wp-blog-header.php');

$result = $wpdb->get_results (
    "SELECT post_id FROM {$wpdb->postmeta} WHERE meta_key = 'YOUR_META_KEY'"
);
if (!empty ($result)) {
    foreach ($result as $row) {
        wp_update_post (array ('ID' => $row->post_id));
    }
}

?>
